a) Field of the Invention
The present invention relates to a vehicular dynamic controlling apparatus and method for an automotive vehicle.
The present invention, particularly, relates to a vehicular dynamic control technique for a vehicular dynamic stability control block to perform a brake force distribution control for each of front or rear tire wheels and/or left or right tire wheels so as to make an estimated value of a yaw rate gain coincident with a target value of the yaw rate gain and a front-wheel steering control block to perform a control over a vehicular yaw rate and lateral motion on the basis of such a vehicular motion (or dynamic) information as a tire cornering force as a result of the brake force distribution control.
b) Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 5-105101 published on Apr. 27, 1993 exemplifies a previously proposed four-wheel steering control apparatus in which a steering angular displacement of each of front and rear tire wheels is controlled so that an actual yaw rate is made coincident with a target yaw rate characteristic.
In the previously proposed four-wheel steering controlling apparatus and method, even when the vehicle is running in a cornering limit running range having a relatively large lateral acceleration of the vehicle, a steering angular displacement of front and rear road wheels are controlled so that the yaw rate generated on the vehicle is made coincident with the target yaw rate characteristic.
Therefore, since the target yaw rate characteristic is made coincident with the generated yaw rate irrespective of a magnitude of the steering angular displacement by the driver, there is a possibility of giving a steering maneuver different from that the vehicular driver desires to the driver.
In addition, there would be a little effect of reducing an understeer tendency by increasing a steering angular displacement of a steering wheel when the vehicle in which the above-described previously proposed control apparatus is mounted is running in the cornering limit running range.
Then, a previously proposed vehicular wheel brake controlling apparatus has been proposed in which a brake force distribution control has been adopted so that an estimated value of a steady state yaw rate gain is made coincident with a target value thereof, thus preventing a spin or drift out even in the cornering limit running range to achieve a desired yaw rate output in response to a steering input by the vehicular driver. The steering input indicates that the vehicular driver has steered a steering wheel of the vehicle.
It is noted that the previously proposed wheel brake controlling apparatus is described in a Japanese Patent Application No. Heisei 10-266542 filed in Japan on Sep. 21, 1998 and does not form a prior art (under 35 U.S.C. 102 and 35 U.S.C. 103).
In the other previously proposed vehicular wheel brake controlling apparatus, the brake distribution control is carried out to make the vehicular steady state yaw rate gain coincident with the target steady state yaw rate gain.
Hence, the tire cornering force in terms of a concept of a circle of friction so that a damping characteristic of the yaw rate becomes reduced as compared with a vehicular normal running condition.
As described above, since a steering maneuver characteristic (steering maneuverability) is varied when the vehicular dynamic stability control is carried out only through the brake force distribution control, there is also the possibility of producing the steering maneuver different from that the vehicular driver has desired to the driver.
It is, therefore, an object of the present invention to provide vehicular dynamic controlling apparatus and method which give a desired yaw rate output in response to the steering input of the vehicular driver even when the vehicle is running in the cornering limit running range without giving the steering maneuver different from that the driver has desired to the driver through a yaw rate damping characteristic which is generally the same as that of the vehicular normal running condition.
The above-described object can be achieved by providing a vehicular dynamic controlling apparatus comprising: a vehicular velocity sensor to detect a vehicular velocity; a steering angular displacement sensor to detect a steering angular displacement of a vehicular steering wheel; a yaw rate sensor to detect a vehicular yaw rate; a yaw rate gain estimating section that estimates a vehicular yaw rate gain from detected values of the vehicular velocity, the yaw rate, and the steering angular displacement; a target yaw rate gain setting section that sets a target value of the yaw rate gain; a brake force distribution controlling section that calculates a brake force command value for each of vehicular front left and right and rear left and right tire wheels to reduce a deviation between an estimated value of the yaw rate gain and the target value thereof; a brake pressure controlling section that controls a brake pressure to be applied to each tire wheel in accordance with the brake force command value for each tire wheel; a tire information calculating section that calculates a tire information related to a vehicular dynamic information on the basis of the brake force for each tire wheel and previously measured tire data; a rear tire wheel steering actuator to be enabled to actuate the rear tire wheels to be steered; a target vehicular dynamical variable calculating section that calculates target vehicular dynamical variables on the basis of the detected values of the vehicular velocity and the steering angular displacement and a target vehicular dynamic model; a rear tire wheel steering angular displacement command value calculating section that calculates a rear tire wheel steering angular displacement command value according to the detected values of the vehicular velocity and the steering angular displacement, the target vehicular dynamical variables, the tire information, and a previously measured controlled vehicular dynamic model; and a rear tire wheel steering angular displacement controlling section that controls an actuation of the rear tire wheel steering angular displacement actuator to make the rear tire wheel steering angular displacement command value coincident with an actual rear tire wheel steering angular displacement.
The above-described object can also be achieved by providing a vehicular dynamic controlling method comprising: detecting a vehicular velocity; detecting a steering angular displacement of a vehicular steering wheel; detecting a vehicular yaw rate; estimating a vehicular yaw rate gain from detected values of the vehicular velocity, the yaw rate, and the steering angular displacement; setting a target value of the yaw rate gain; calculating a brake force command value for each of vehicular front left and right and rear left and right tire wheels to reduce a deviation between an estimated value of the yaw rate gain and the target value thereof; controlling a brake pressure to be applied to each of the tire wheels in accordance with the brake force command value for each tire wheel; calculating a tire information related to a vehicular dynamic information on the basis of the brake force for each tire wheel and previously measured tire data; calculating target vehicular dynamical variables on the basis of the detected values of the vehicular velocity and the steering angular displacement and a target vehicular dynamic model; calculating a rear tire wheel steering angular displacement command value according to the detected values of the vehicular velocity and the steering angular displacement, the target vehicular dynamical variables, the tire information, and a previously measured controlled vehicular dynamic model; and controlling an actuation of a rear tire wheel steering angular displacement actuator to make the rear tire wheel steering angular displacement command value coincident with an actual rear tire wheel steering angular displacement.